ORIGINAL ARTICLE Positive correlation between type 1 and 2 iodothyronine deiodinases activities in human goiters Valmara S. Pereira • Michelle P. Marassi • Doris Rosenthal • Ma ´rio Vaisman • Va ˆnia M. Corre ˆa da Costa Received: 8 August 2011 / Accepted: 14 December 2011 / Published online: 30 December 2011 Ó Springer Science+Business Media, LLC 2011 Abstract Type 1 (D1) and 2 (D2) iodothyronine deio- dinases are selenocysteine-containing enzymes that cata- lyze the deiodination of T4 to T3 in the thyroid and in peripheral tissues. Despite their importance to the plasma T3 pool in human beings, there are few studies about their behavior in human thyroids. In order to better understand iodothyronine deiodinase regulation in the thyroid gland, we studied thyroid tissue samples from follicular adenoma (AD, n = 5), toxic diffuse goiter (TDG, n = 6), nontoxic multinodular goiter (NMG, n = 40), papillary thyroid carcinoma (PTC, n = 8), and surrounding normal tissues (NT, n = 7) from 36 patients submitted to elective thy- roidectomy. D1 and D2 activities were determined by quantification of the radioiodine released by 125 I-rT3 or 125 I-T4 under standardized conditions, and expressed as pmol rT3 deiodinated per minute and mg protein (pmol rT3 min -1 mg -1 ptn) and fmol T4 deiodinated per minute and mg protein (fmol T4 min -1 mg -1 ptn), respectively. D1 activity detected in TDG and AD tissues were signifi- cantly higher than in NT, PTC or NMG samples. D2 activity was also significantly higher in TDG and AD samples than in PTC, NMG, or NT. There was great var- iability in D1 and D2 enzymatic activities from distinct patients as well as from different areas from the same goiter. There was a positive correlation (P \ 0,0001, r = 0.4942) between D1 and D2 activities when all sam- ples were taken into account, suggesting that—in the thy- roid—these two iodothyronine deiodinases may have related regulatory mechanisms, even if conditioned by other as yet unknown factors. Keywords Human goiters Á Type 1 iodothyronine deiodinase Á Type 2 iodothyronine deiodinase Á Positive correlation Introduction Type 1 iodothyronine deiodinase (D1) and type 2 iodo- thyronine deiodinase (D2) catalyze T4 activation, and both isoforms are present in human thyroid tissue [1]. Liver and kidney D1 activity is known to decrease in hypothyroidism while, in contrast, D2 increases in pituitary, brain and brown adipose tissue. Thyroid function is normally unal- tered in patients with thyroid carcinomas but in most dif- ferentiated thyroid carcinomas there is a decrease in function compared to normal thyroid tissue, although they continue to produce thyroglobulin (Tg), which can be iodinated and form T 3 and T 4 . The human thyroid gland is morphologically and functionally heterogenous, and even when exposed to the same amounts of thyrotropin (TSH) follicular cells behave differently. D2 is highly expressed in Graves’ disease thyroid tissue and in some adenomas (ADs) in which it may contribute to the relatively high circulating T3 serum level [2]. A high activity of D2 has Electronic supplementary material The online version of this article (doi:10.1007/s12020-011-9587-6) contains supplementary material, which is available to authorized users. V. S. Pereira Á M. P. Marassi Á D. Rosenthal Á V. M. Corre ˆa da Costa (&) Laborato ´rio de Fisiologia Endo ´crina Doris Rosenthal, Instituto de Biofı ´sica Carlos Chagas Filho, Universidade Federal do Rio de Janeiro, CCS, bloco G, Cidade Universita ´ria, Ilha do Funda ˜o, Rio de Janeiro 21949-900, Brazil e-mail: vmccosta@biof.ufrj.br M. Vaisman Servic ¸o de Endocrinologia, Hospital Universita ´rio Clementino Fraga Filho, Universidade l do Rio de Janeiro, CCS, bloco G, Cidade Universita ´ria, Ilha do Funda ˜o, Rio de Janeiro 21949-900, Brazil 123 Endocrine (2012) 41:532–538 DOI 10.1007/s12020-011-9587-6